1. Field of the Invention
The present invention relates to rigid PVC formulations containing ethylene-propylene copolymers. More particularly, the present invention relates to the use of ethylene-propylene copolymers to reduce gloss and improve PVC characteristics, such as heat and UV stability, lubricity, and coloration.
2. Description of Related Art
An overview of the lubricants used in plastics and their functions in plastics processing is given in R. GACHER AND H. MULLER, PLASTICS ADDITIVES HANDBOOK, (4th ed. 1993), and HANS ZWEIFEL, PLASTICS ADDITIVES HANDBOOK (5th ed. 2001). Their functions include improving the compound flow by reducing internal friction and preventing adhesion of polymer melts to hot machine parts (release effect). Lubrication affects the heat stability of PVC. Traditional lubricants are obtained using conventional vanadium/aluminum Ziegler catalysts and include polyolefin waxes, such as ethylene homopolymers and its copolymers with propylene or α-olefins.
There are several patents relating to processes and, more specifically, catalysts for manufacturing liquid ethylene-α-olefin copolymers and, more specifically, ethylene-propylene co-polymers (EPM), optionally containing a non-conjugated diene. Examples include U.S. Pat. Nos. 3,896,094, 3,896,096, 4,668,834, 4,956,122, 4,960,829, 5,527,951, and 5,786,504. Typically, such catalyst compositions include:
(a) a vanadium-containing compound, a catalyst;
(b) an organoaluminum compound, a co-catalyst; and
(c) a catalyst activator/promoter.
The presence of the catalyst activator/promoter differentiates this tri-component catalyst system from the conventional vanadium/aluminum Ziegler catalysts used, for example, for making standard polyethylene waxes and allows producing ethylene-propylene copolymers in a liquid form.
U.S. Pat. No. 3,896,094 discloses that vanadium phosphorodithioates, represented by a specified formula, are effective catalysts in the preparation of copolymers of alpha-olefins, e.g., ethylene/propylene rubber (EPR), and the terpolymers of the alpha-olefins with the nonconjugated dienes, e.g., ethylene/propylene/diene terpolymers (EPDM rubber), when an alkyl aluminum is used as a cocatalyst. These catalyst systems are said to be very efficient and can be modified with a zinc compound to give liquid elastomers.
U.S. Pat. No. 3,896,096 discloses that in the copolymerization of alpha-olefins, especially the copolymerization of ethylene and propylene (with a diene if desired), using a coordination type catalyst based on a vanadium salt and an alkylaluminum halide, the molecular weight of the polymer can be regulated, and the activity of the catalyst can be enhanced, by adding disulfides of a defined type.
U.S. Pat. No. 4,668,834 discloses that low molecular weight copolymers comprised of ethylene, an alpha-olefin and (optionally) a nonconjugated polyene, which copolymers have a viscosity index of at least about 75 and vinylidene-type unsaturation, possess unexpected advantages as intermediates in epoxy-grafted electrical encapsulation compositions.
U.S. Pat. No. 4,956,122 discloses a lubricating composition containing: a high viscosity synthetic hydrocarbon such as high viscosity poly(alpha-olefins), liquid hydrogenated polyisoprenes or ethylene-alpha-olefin copolymers having a viscosity of 40 to 1000 centistokes at 100° C.; a low viscosity synthetic hydrocarbon and/or optionally a low viscosity ester; and optionally an additive package to impart desirable performance properties to the composition.
U.S. Pat. No. 4,960,829 discloses that blends comprised of (a) a high molecular weight elastomeric polymer; (b) a sufficient amount of an ethylene/alpha-olefin/nonconjugated polyene terpolymer having a number average molecular weight of between about 1,000 and about 15,000 such that the variety of the blend is at least about 5 percent lower than the viscosity of component (a) alone, and (c) a curative, exhibit increased processability and, when cured, exhibit unexpectedly desirable tensile strength, ozone resistance, and oil resistance.
U.S. Pat. No. 5,527,951 discloses that tert-alkylmethoxy-substituted vanadium compounds are useful as catalysts for the polymerization of ethylene or the copolymerization of ethylene with alpha-olefins and (optionally) nonconjugated polyenes.
U.S. Pat. No. 5,786,504 discloses compounds of a specified formula that by themselves and in combination with certain halo-but-2-enoic acids and esters are useful as catalyst promoters in ethylene polymerization processes.
U.S. Published Patent Application 2003/0114322A1 discloses the use of polyolefin waxes as external lubricants and release agents for plastics. The polyolefin waxes are produced by using metallocene catalysts, whereby the polyolefin waxes are homopolymerizates of ethylene or are copolymerizates of ethylene with one or more 1-olefins, and linear or branched, substituted or non-substituted olefins having 3-18 C atoms are used as 1-olefins. The processable plastic mixtures produced in this manner are said to have a distinctively longer tack-free time and exhibit an improved behavior with regard to mold release.
Belgian Patent No. 809104 relates to a pipe composition of reduced cracking and increased toughness that was obtained via graft copolymerization from 95 parts vinyl chloride monomer and five parts rubbery ethylene-propylene copolymer.
Chinese Patent No. 1475339 relates to a tubing core composition containing 100 parts PVC and 10-40 parts of ethylene-propylene rubber as an impact modifier.
European Patent Application 0182470 relates to low molecular weight, liquid EPDM (ethylene-propylene terpolymers containing non-conjugated dienes) compositions suitable for weatherable coatings based on asphalt, polyurethanes, and solid EPDM. The compositions are comprised of a copolymer of ethylene and a monomer having the formula CH2CHR, where R is C1-C10 linear or branched alkyl (propylene is preferred), and optionally containing a non-conjugated diene, such as 1,4-hexanedione; said polymer having a molecular weight of 500-20,000. The ethylene to propylene (E/P) ratio is from 85:15 to 25:75, with the preferred ratios being 60:40 to 40:60. The non-conjugated diene in the EPDM is present in a range of from 0 to 25 percent, with a preferred range of 5 to 13 percent. The compositions include a reinforcing agent, a curative (such as organic peroxides) to convert double bonds of EPDM into the cured, fully saturated and weatherable polymer, and a small amount of a solvent. The compositions contain conventional adjuvants: antioxidants, antiozonates, ultraviolet stabilizers, tackifiers, lubricants, pigments, fillers, flame retardants, and the like. The preparation of the preferred EPDM materials is described in U.S. Pat. Nos. 3,819,592, 3,819,852, 3,896,094, and 3,896,096.
Truly rigid formulations containing less than 10 phr (parts of the liquid EPM per 100 parts PVC resin) and applications for such formulations are believed to be new in the art and heretofore undisclosed.